RF switches are key elements used in RF systems including communications and radars. RF switches enable low-loss, low-noise, fast, linear signal routing. They may also be used for impedance tuning and phase shifting. Due to varying system RF power handling requirements, it is important that an RF switch have linear performance from approximately a milli-watt (mW) to a watt level. While micro-electromechanical (MEMS) switches have been demonstrated in the prior art for RF systems with the desired low-loss, low-noise, isolation, linearity, and adequate power handling properties, these prior art RF switches have high switching voltage (30-70 V) requirements, low reliability and packaging issues. Thus, even after the decades of research, RF-MEMS switches are not commonly found in RF systems.
Monolithic microwave integrated circuit (MMIC) integration has in general been limited due to the size and high voltage requirements of prior art RF-MEMS switches, and mobile platform applications are very difficult to realize due to the high switching voltage requirements.
In the prior art Chua et al., “Low resistance, high dynamic range reconfigurable phase change switch for RF applications”, Applied Physics Letters vol. 97, 183506, (2010) mentions using PCM material for RF switches; however, Chua does not describe an RF switch design using PCM materials. Lo et al., “Three-terminal probe reconfigurable phase-change material switches”, IEEE Transactions on Electron Devices., vol. 57, p. 312, (2010) describes a switch with a three-terminal layout, consisting of an array of sub-vias; however, in Lo the switching is performed using external probes. Wen et al., “A phase-change via-reconfigurable on-chip inductor”, IEDM Tech digest, (2010) describes via structures with GeTe material, with an Ron of 1.1 ohm and an Ron/Roff of 3×104; however, in Wen the switching is also performed using external probes.
The principal of PCM has been known since the 1960s. Rewritable optical DVDs have been developed using Ge2Sb2Te5, and also using (Ag or In)Sb2Te. Lately, phase change materials have been being developed for non-volatile memory, as a future replacement of flash memory. Companies involved in these developments include Micron, Samsung, IBM, STMicroelectronics, and Intel. Following are recent publications on use of PCMs for digital applications: EE Times, November, 2011, “Samsung preps 8-Gbit phase-change memory”, Perniola et al”, “Electrical behavior of phase change memory cells based on GeTe”, IEEE EDL., vol. 31, p. 488, (2010).
What is needed are RF switches using phase-change materials that are compatible with conventional semiconductor RF integrated circuit (RFIC) and MMIC processes. The embodiments of the present disclosure answer these and other needs.